Sunday, April 13, 2014

Skyline/Goldwing Sbach 60" Build Day #3

Today I essentially completed the Sbach 60" (it's called a 70 for some reason, maybe the nitro engin size?). But like a building that's not done until the capstone is set in place, my Sbach isn't really done until the spinner is put on, and I still have some of the decals to put on.

First of all, today's minor annoyance. The wing securing screws are plastic, and the right wing one was stripped because the nut embedded in the wing was obstructed. When the packer put the screw in it stripped, so I had to replace it. It was M5, so I picked up a couple M5 cap screws at Home Depot. in the pic above, the left one is original, the middle the M5 cap screw, and the last the hybrid I made. I cut the plastic screw with a small tab left, which. I shaped it to fit in the hex top of the cap screw, applied some superglue and joined them. The cap screw top is a bit small to screw into the wing, so the thumb accessible top is nice. It's not supposed to be gorilla-tight, so doesn't need to tolerate a whole lot of torque. I was able to clear the obstruction with a cap screw. Works fine!

Major project for today is the cowl. I created a paper mock up and had marked the cowl bolt holes where I wanted them, midline and 10mm below the top and bottom edge. drilled the pilot holes.

The end of the fuse where the bolts will go before drilling.

Pilot holes drilled. Stepped up to 3 mm.

I used a trick I learned from building my Eflite Stearman (still have another one of those NIB) to transfer the holes in the fuse to the holes to the cowl. I tape a piece of paper or card to the side of the fuse and poke a hole through the paper into the drilled fuse hole. Place and center the cowl and drill a pilot hole into the cowl using the paper template.

I thought I had pics of how I set up the nuts inside the fuse. I didn't want to use servo wood screws which weaken over time, so I took M3 flat nuts and washers and fixed them into place. I inserted the M3 bolt just deep enough for the washer and nut to secure, with a small tip beyond. I used a small piece of hard wood to wedge between a flat spot on the nut and the firewall to hold it against torque and super glued it in place. I then set each one in epoxy. Once it dried I popped the bolt through the epoxy. I could of used those self wedging nuts with teeth, but I didn't have any and could find M3 sized ones at Home Depot. Once I had set the cowl in place, I used rubber grommets from my heli stock and used them to protect the fiberglass cowl. I had M3 fiber washers but I had changed my mind and used M4 bolts.

Cowl in place and all done. The prop plate is about 2mm forward of the front edge of the cowl. Perfect. Came out precisely centered (I set the motor without any offset)..

Put a couple of the stickers on, will finish those later. Once the spinner is on, I'll put the whole thing together and take some picks.

About Me

Men fear thought as they fear nothing else on earth -- more than ruin -- more even than death.... Thought is subversive and revolutionary, destructive and terrible, thought is merciless to privilege, established institutions, and comfortable habit. Thought looks into the pit of hell and is not afraid. Thought is great and swift and free, the light of the world, and the chief glory of man. ~ Bertrand Russell